It is possible to do even better/easier in TinyMCE 4.0. We can set the allowed_elements without worrying that some internals would break.

However the usefulness of this is quite limited. Kses was fixed/expanded several times since this ticket. Generally by default the users cannot add "forbidden" tags and attributes, so this would apply only for plugins that extend the editor and only in certain cases. Also, we cannot stop the users adding arbitrary content in the Text editor.

Thinking this is something we can revisit in the future if a need arises.